Chapter 8-Overall Flow of EnergySunlightGreen Plant Cell (Photosynthesis) Glucose Metabolism of glucose ATP-Concept 8.1Metabolism: totality of organism’s chemical reactionsMetabolism is an emergent property of life.-Metabolic PathwaysBegins with a specific molecule and ends with productA specific enzyme catalyzes each stage.Catabolic Pathways: Release energy by breaking down complex molecules into simpler compounds.Ex. Cellular respiration: the breakdown of glucose in the presence of oxygen.Anabolic Pathways: consume energy to build complex molecules from simpler ones. Ex. The synthesis of protein from amino acids is an example of anabolism.Bioenergetics: Study of how organisms manage their energy sources.-Forms of EnergyEnergy: Capacity to cause change.Potential Energy: energy due to location or structure.Kinetic Energy: Energy due to motion.-Laws of energy transformationThermodynamics is the study of energy transformation.Organisms are open systems.-First law of thermodynamics Energy is a constantEnergy can be transferred or transformed byt not created or destroyed.Also known as the principle of conversation of energy.-Second Law of thermodynamicsDuring transfer, some is unusable and is lost as heat.Every energy transfer of transformation increases the entropy of the universe.Energy (G) change in free change (Delta G)Living organisms convert organized forms of energy to eat.Spontaneous processes occur with out energy input, they can happen quickly or slowlyFor a process to occur without energy input they must increase entropy in the universe. -Biological order and disorderCells create ordered structures from less ordered materials.Organisms also replace ordered forms of matter and energy with less ordered forms.Evolution of more complex organisms does not violate the 2nd law of thermodynamicsEntropy may decrease in an organism but total entropy will increase in theuniverse.In order to decrease entropy in an organism, that organism needs to create more complex structures, which require energy, heat is lost.-Concept 8.2Biologists want to know which reactions occur spontaneously and which require input of energy.Must determine energy changes that occur in chemical reactions.-Free EnergyEnergy that can do work, holding temperature and pressure constantSpontaneous reactions can be harnessed to preform work.Delta G= Delta H – Temperature (Delta S)Delta G= Gf – GiNon-Spontaneous, EndothermicIf Gf>GiThen Delta G>0 Spontaneous, ExothermicIf Gf<GiThen Delta G<0-Free Energy and MetabolismThe concept of free energy can be applied to the chemistry of life’s processes.Exergonic reaction: Releases energy, spontaneous.Endergonic Reaction: Absorbs energy, non-spontaneous.-Maltose SynthesisReaction is not spontaneous and requires energy, endergonic-Maltose BreakdownReaction is spontaneous and releases energy, exergonic-General rule of reactionBreaking of molecules apart by hydrolysis causes:1)- Delta G2) Spontaneous and exergonicForming molecules through dehydration reactions1) + Delta G2) Non-spontaneous and endergonicEquilibrium and MetabolismReactions in closed systems eventually reach equilibrium and then do no work.Life Metabolism is never t equilibrium.Cells are not at equilibrium-Concept 8.3: ATP powers cellular work by coupling exergonic reactions to endergonic reactions.A cell does three kinds of work1) Chemical2) Transport3) MechanicalMost energy coupling in cells is mediated by ATP.-Structure and Hydrolysis of ATPAdenosine triphosphate is the cell’s energy shuttle.ATP is (Ribose Sugar), Adenine (Nitrogen Base and 3 phosphate groups.Bonds between phosphate groups of ATP’s tails can be broken through hydrolysis.ATP drives endergonic reactions by phosphorylation, transferring phosphate group to other molecules.Recipient is called a phosphorylated intermediateAllows for coupling of exergonic and endergonic reactions. Bonds between phosphate groups contain high potential energy from a repulsion of (-) charge between oxygens on the phosphate group.-How the Hydrolysis of ATP preforms workOverall, the couple reactions are exergonic.3 types of cellular work are powered by hydrolysis of ATPGlucose + Glucose + ATP Maltose + ADP + PO4The phosphorylated intermediate is more reactive (less stable) than the original phosphorylated molecule.-The Regeneration of ATPATP is a renewable resource that is regenerated by addition of a phosphategroup to adenosine di phosphate.Potential energy is stored in this bond.ATP drives most cellular work ATP ADP + Phosphate group.ATP cycle is a revolving door through which energy passes during transfer from catabolic to anabolic pathways.-Metabolic PathwaysMetabolic pathway begins with a specific molecule and ends with a product.Each step is catalyzed by a specific enzyme2 questions about cell reactions.Will a reaction occur spontaneously or will extra energy be required? What is the speed of the reaction?-Concept 8.4: Enzymes speed up metabolic reactions by lowering energy barriersA catalyst is a chemical agent that speeds up reactions without being consumedEnzyme as a catalytic proteinHydrolysis of sucrose by the enzyme Sucrase is an example of an enzyme-catalyzed reaction. Sucrase can also drive the reaction in the opposite direction. -Activation Energy barrierEvery chemical reaction between molecules involves the breaking and forming of bonds.Initial energy needed to start a chemical reaction is called free energy of activation or Activation Energy or EA Activation energy is often supplied in the form of thermal energy.When the molecules gain enough energy and become unstable they enter the transition state.-Enzymes and Energy BarrierEnzymes catalyze reactions by lowering the activation energy barrierInstead of using high temperature, which would denature proteins and kill cells.Enzymes do not affect the change inn free energy (Delta G) instead they hasten reactions that would occur eventually.Enzyme cannot change an endergonic reaction into an exergonic one.Can catalyze reaction in both ways, but always toward –Delta G and toward equilibrium.Enzyme substrate is its molecule that it can catalyze. -Substrate Specification Enzymes Enzyme binds with substrate called
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